Integrated Circuit Packages, Methods of Forming Integrated Circuit Packages, And Methods of Assembling Integrated Circuit Packages

ABSTRACT

Some embodiments include methods of assembling integrated circuit packages in which at least two different conductive layers are formed over a bond pad region of a semiconductor die, and in which a conductive projection associated with an interposer is bonded through a gold ball to an outermost of the at least two conductive layers. The conductive layers may comprise one or more of silver, gold, copper, chromium, nickel, palladium, platinum, tantalum, titanium, vanadium and tungsten. In some embodiments, the bond pad region may comprise aluminum, an inner of the conductive layers may comprise nickel, an outer of the conductive layers may comprise gold, the conductive projection associated with the interposer may comprise gold; and the thermosonic bonding may comprise gold-to-gold bonding of the interposer projection to a gold ball, and gold-to-gold bonding of the outer conductive layer to the gold ball. Some embodiments include integrated circuit packages.

RELATED PATENT DATA

This patent claims priority to Singapore Patent Application No.200703582-7, which was filed May 17, 2007, and which is titled“INTEGRATED CIRCUIT PACKAGES, METHODS OF FORMING INTEGRATED CIRCUITPACKAGES, AND METHODS OF ASSEMBLING INTEGRATED CIRCUIT PACKAGES”.

TECHNICAL FIELD

Integrated circuit packages, methods of forming integrated circuitpackages, and methods of assembling integrated circuit packages.

BACKGROUND

Integrated circuit packages may be formed as flip chip assemblies.Specifically, a semiconductor die may be bonded face-down (“flipped”)onto an interposer. An example prior art process for forming a flip chipassembly is described with reference to FIGS. 1 and 2.

FIG. 1 shows a semiconductor die 10 in face-down orientation, and showsan interposer 12 beneath the die.

The semiconductor die 10 comprises a base 14 supporting a plurality ofbond pad regions 16. The base 14 may comprise a semiconductor material(for instance, monocrystalline silicon) supporting any of numerousintegrated circuit components, including, for example, memorycomponents, logic components, sensor components, wiring, etc.. Thevarious components are not shown in order to simplify the drawing.

Bond pad regions 16 provide electrical connection from integratedcircuit components associated with base 14 to circuitry external of thebase. The bond pad regions may comprise, consist essentially of, orconsist of aluminum or copper. The bond pad regions are shown to haveouter surfaces 17, and electrical interconnect material 18 is shownbonded to such outer surfaces. The electrical interconnect material maycomprise, consist essentially of, or consist of gold, and may be balls(as shown) bonded to the bond pad regions, or may be pieces of wirebonded to the bond pad regions.

The bond pad regions 16 may be distributed in numerous orientationsacross a surface of die 10. For example, the bond pad regions may beso-called inner bond pad regions along a central portion of the diesurface, may be so-called outer bond pad regions along non-centralportions of the die surface and connected to the inner bond pad regionsby redistribution layers, or maybe a combination of inner bond padregions and outer bond pad regions.

Interposer 12 comprises a board 20 and electrical interconnects 22supported on an upper surface of the board. The interposer alsocomprises electrical interconnects 24 supported on a lower surface ofthe board. Various wiring (not shown) may extend through the board toconnect various electrical interconnects 22 with various electricalinterconnects 24. The electrical interconnects 22 are ultimately bondedto semiconductor die 10 to form an integrated circuit package comprisingthe die and interposer, and the electrical interconnects 24 areultimately utilized for electrical connection of the package to othercircuitry.

Electrical interconnects 22 may comprise, consist essentially of, orconsist of gold. Electrical interconnects 24 may comprise any suitableelectrically conductive materials or combinations of materials, and may,for example, comprise materials suitable for bonding to solder.

FIG. 2 shows the interposer 12 bonded to the semiconductor die 10. Thebonding may comprise gold-to-gold bonding between gold-containinginterconnects 22 and gold-containing interconnects 18. The gold-to-goldbonding is accomplished by pressing interconnects 18 and 22 togetherwhile subjecting the interconnects to ultrasonic energy and thermalenergy (so-called thermosonic bonding). An underfill 30 is provided in agap between die 10 and interposer 12. The underfill may comprise a filmor paste, and may, for example, comprise non-conductive paste (NCP),anisotropic conductive paste (ACP), anisotropic conductive film (ACF) ororganic solderability preservative (OSP).

A problem that can occur is that the bonding between interconnects 18and 22 may subject bond pad regions 16 to sufficient pressure to causecracking 32 (only some of which is labeled in FIG. 2) or other defectswithin the bond pad regions. Another problem that may occur is that thethermosonic energy of the thermosonic bonding may cause cratering orother defects in the bond pad regions. Yet another problem that mayoccur is that the bonding of interconnects 18 to the bond pad regions 16to form the semiconductor die construction of FIG. 1 may induce defectswithin regions 16.

It is desired to develop new methods for assembling integrated circuitpackages which avoid some or all of the above-described problems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of a semiconductor die and interposer at a stage of aprior art process for assembling an integrated circuit package.

FIG. 2 is a view of the semiconductor die and interposer of FIG. 1 shownat a prior art processing stage subsequent to that of FIG. 1.

FIGS. 3-9 illustrates a process for preparing a semiconductor die forassembly into an integrated circuit package.

FIGS. 10 and 11 illustrate a process for assembling an integratedcircuit package comprising the semiconductor die of FIGS. 3-9 and aninterposer.

FIG. 12 shows a portion of an integrated circuit package comprising abond between a bond pad region and an interconnect of an interposer inaccordance with an embodiment.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Some embodiments include methods of providing materials across bond padsto protect the pads during subsequent thermosonic bonding. Suchmaterials may prevent, or at least substantially reduce, one or more ofthe problems discussed above in the “Background” section of thisdisclosure. An example embodiment for forming an integrated circuitpackage is described with reference to FIGS. 3-11.

Referring initially to FIG. 3, such illustrates a semiconductor die 50comprising the base 14 and bond pad regions 16 discussed above withreference to the prior art semiconductor die 10 of FIG. 1. The base may,as discussed above regarding FIG. 1, comprise integrated circuitrycontaining memory, logic, sensors, etc..

The bond pad regions 16 are shown to have outermost surfaces 17. In someembodiments, the bond pad regions may comprise, consist essentially of,or consist of aluminum or copper; and accordingly the outermost surfacesmay comprise, consist essentially of, or consist of aluminum or copper.If the bond pad regions contain aluminum, a thin oxide of aluminum (notshown) may extend across the uppermost surfaces 17 at the processingstage of FIG. 3.

Referring to FIG. 4, zinc-containing layers 52 are formed over bond padregions 16. The zinc-containing layers may be formed by first cleaningthe bond pad regions with acid (for example, one or both of sulfuricacid and hydrofluoric acid) and/or base (for example, sodium hydroxide).Such cleaning forms a fresh surface for deposition of zinc, and mayremove oxide. Subsequently, the surface may be exposed to zincate (inother words, to a zinc-containing solution, which may be, for example,cyanide-based, acid-based or alkaline-based) to deposit thin layers ofzinc (which may be monolayers) across the surfaces of the bond padregions. In some embodiments, the layers of zinc initially formed acrossthe bond pad region surfaces may have relatively large grain sizes, andmay be utilized as sacrificial layers to prepare the surfaces forsubsequent deposition of zinc-containing layers with a smaller grainsizes. Accordingly, the first zinc-containing layers may be removed withan acid (for example, nitric acid) to again expose surfaces 17 of bondpad regions 16 (FIG. 5), and then second zinc-containing layers 54 (FIG.6) may be formed by another exposure of the bond pad region surfaces tozincate.

The zinc-containing layers 54 are formed directly against the conductivematerial (for example, aluminum or copper) of the bond pad regions inthe shown embodiment of FIG. 6. Zinc-containing layers 54 may beconsidered examples of adhesion layers for adhering subsequently-formedlayers (for instance, the layers 56 discussed below with reference toFIG. 7) to the bond pad regions. The zinc-containing layers are examplesof adhesion layers, and other materials may be utilized for adhesionlayers in other embodiments. For instance, zinc-containing layers workwell for aluminum-containing surfaces, but may not work satisfactorilyfor copper-containing surfaces. Accordingly, palladium-containingadhesion layers may be utilized when the bond pad regions comprisecopper. In other embodiments, the bond pad regions may comprisematerials other than copper or aluminum, and the adhesion layers maycomprises materials other than, or in addition to, one or both of zincand palladium.

Referring next to FIG. 7, metal-containing layers 56 are formed over anddirectly against the adhesion layers 54. The metal-containing layers maycomprise one or more of Co, Cr, Ni, Pt, Ta, Ti, V and W; and may bedoped with one or both of boron and phosphorous. For instance, layers 56may comprise nickel deposited utilizing electroless depositionmethodology. In some embodiments, layers 56 may consist essentially of,or consist of such nickel; and in other embodiments layers 56 mayconsist essentially of, or consist of such nickel doped with phosphorous(the phosphorus may be present at a concentration of from about 7 atomicpercent to about 11 atomic percent).

Referring to FIG. 8, electrically conductive layers 58 are formed overand directly against electrically conductive layers 56, and balls 18 areformed directly against the conductive layers 58. The electricallyconductive layers 58 may, for example, comprise, consist essentially of,or consist of one or more of Ag, Au, Cu and Pd. Such materials may beformed by immersion methodologies, and may be doped with phosphorous orboron. For instance, the layers 58 may comprise Pd doped withphosphorous to a phosphorous concentration of from about 7 atomicpercent to about 11 atomic percent. In particular embodiments, layers 56may comprise, consist essentially of, or consist of nickel or nickeldoped with phosphorus; and layers 58 may comprise, consist essentiallyof, or consist of gold. The layers 56 and 58 may together comprise athickness of from about 0.1 micron to about 10 microns.

The balls 18 utilized in FIG. 8 may comprise any of various electricallyconductive materials, including, for example, copper or gold. The ballsmay thus comprise conventional compositions of the type described in the“Background” section of this disclosure, or may comprisenon-conventional compositions. In some embodiments, the balls will notcomprise solder, and specifically will not comprise indium or tin.

Layers 54, 56 and 58 form electrically conductive stacks over bond padregions 16. The stacks extend across the entire upper surfaces of thebond pad regions, and may be considered protective electricallyconductive caps formed across the bond pad regions. Although suchelectrically conductive caps are shown to comprise only the three layers54, 56 and 58 in the embodiment of FIGS. 3-8, in other embodiments oneor more additional layers may be inserted between adhesion layer 54 andconductive layer 56, and/or between conductive layer 56 and conductivelayer 58. For instance, the conductive stacks may comprise Ni/Pd/Au(with layers 56 and 58 being Ni and Au, respectively, and the layer ofPd being provided between them).

Since conductive layers 58 are outward of conductive layers 56 relativeto bond pad regions 16; the layers 56 may be referred to as innerconductive layers, and the layers 58 as outer conductive layers, in someembodiments.

The layers 58 are shown to comprise outermost surfaces 59. Balls 18 arebonded to the outermost surfaces 59 of layers 58. The bonding of theballs to layers 58 may be accomplished with any suitable methodology,such as, for example, thermosonic bonding. Balls 18 may comprise,consist essentially of, or consist of copper or gold; and in someembodiments the outermost surfaces 59 may comprise, consist essentiallyof, or consist of copper or gold.

Referring to FIG. 9, deformable material 60 is formed across base 14,across balls 18, and across surfaces 59 of layers 58. Deformablematerial 60 is ultimately utilized as an underfill material of a flipchip construction comprising semiconductor die 50, and may, for example,comprise one or more of a non-conductive film, non-conductive paste,anisotropically conductive film (so-called z-axis film), anisotropicallyconductive paste (so-called z-axis paste), and organic solderabilitypreservative (OSP).

Referring to FIG. 10, semiconductor die 50 is inverted and providedproximate another structure separate from the die, with such otherstructure corresponding to an interposer 12 of the type described abovewith reference to prior art FIGS. 1 and 2. The interposer comprises thebase 20 and interconnects 22 and 24 described above. The interconnects22 may comprise, consist essentially of, or consist of copper, silver,palladium or gold; and comprise outer conductive surfaces 23. Theinterconnects 22 may be considered to correspond to electricallyconductive projections or bumps in some embodiments.

Although die 50 is shown inverted in the embodiment of FIG. 10, in otherembodiments die 50 may remain in the orientation of FIG. 9 andinterposer 12 may be inverted. Also, although underfill 60 is shownformed across a surface of the die, in other embodiments some or all ofthe underfill may be formed across surfaces associated with interposer12 at the processing stage of FIG. 10. For instance, if material 60comprises OSP, such may be provided across outermost surfaces ofinterconnects 22 at the processing stage of FIG. 10. In yet otherembodiments, the underfill may be omitted, or provided at a processingstage subsequent to that of FIG. 10.

Although balls 18 are shown bonded to conductive layers 58, in otherembodiments the balls may be instead bonded to the interposer at theprocessing stage of FIG. 10.

Referring to FIG. 11, surfaces 23 of interposer 12 are pressed throughdeformable material 60 to directly contact balls 18. Once surfaces 23and balls 18 are in contact, interconnects 22 may be bonded to the ballsutilizing vibrational and/or thermal energy. The vibrational energy maybe provided to comprise a frequency of at least about one kilohertz, andthe thermal energy may correspond to a temperature of at least aboutroom temperature. In some embodiments, the bonding may comprisethermosonic bonding at a temperature of from about room temperature(about 22° C.) to about 300° C. (for example, from about roomtemperature to about 200° C.); and with a vibrational energy having afrequency of from about one kilohertz to about 240 kilohertz (forexample, a frequency of from about 40 kilohertz to about 100 kilohertz,such as a frequency of about 60 kilohertz); and for a time of less thanabout five seconds (for example, for a time of about three seconds). Inembodiments in which balls 18 initially contact surfaces 23 ofprojections 22 (in other words, contact surfaces 23 at the processingstage of FIG. 10 instead of contacting surfaces 59 of layers 58), thebonding may be accomplished with the same combination of vibrationaland/or thermal energy discussed above, but will bond the balls tosurfaces 59. In other embodiments, balls 18 may be omitted, and thevibrational and/or thermal energy may be utilized to directly bondsurfaces 23 of projections 22 to surfaces 59 of layers 58.

FIG. 11 shows surface 23 of interconnect 22 being planar, surface 59 ofouter conductive layer 58 also being planar, and balls 18 being bondedto the planar surfaces. Such leaves gaps adjacent locations where theballs contact the planar surfaces, as shown in FIG. 12. Specifically,FIG. 12 shows a portion of an integrated circuit package 100 comprisingthe various structures and layers described above with reference toFIGS. 3-11, but comprising a gap 102 identified between a surface of aball 18 and a portion of surface 59 of outer conductive layer 58. Insome embodiments, it can be advantageous to utilize z-axis conductivematerial (for example, anisotropically conductive film or paste) withinunderfill 60 so that the material 60 compressed between the surfaces ofthe ball and outer conductive layer 58 within gap 102 becomes conductivealong the axis of compression (in other words, along a shown axis 110extending within the gap between surface 59 and the ball). Theconductivity of material 60 within the gap may then provide improvedelectrical connection between conductive layer 58 and interconnect 22relative to that which would occur in the absence of conductivity ofmaterial 60. Gaps similar to gap 52 are along all locations where planarsurfaces 23 and 59 join to balls 18.

In compliance with the statute, the subject matter disclosed herein hasbeen described in language more or less specific as to structural andmethodical features. It is to be understood, however, that the claimsare not limited to the specific features shown and described, since themeans herein disclosed comprise example embodiments. The claims are thusto be afforded full scope as literally worded, and to be appropriatelyinterpreted in accordance with the doctrine of equivalents.

1. A method of assembling an integrated circuit package, comprising:providing a semiconductor die comprising integrated circuitry, the diecomprising electrically conductive bond pad regions and electricallyconductive caps over an entirety of the bond pad regions; providing aninterposer having electrically conductive projections; and bonding theelectrically conductive projections to the electrically conductive capsutilizing vibrational energy having a frequency of at least about onekilohertz.
 2. The method of claim 1 wherein the bonding comprises:providing electrically conductive structures between the electricallyconductive projections and the electrically conductive caps; directlybonding the electrically conductive structures to the electricallyconductive projections; and directly bonding the electrically conductivestructures to the electrically conductive caps.
 3. The method of claim 2wherein the electrically conductive structures comprise copper or gold.4. The method of claim 1 wherein the bonding comprises: providinggold-containing material between the electrically conductive projectionsand the electrically conductive caps; directly bonding thegold-containing material to the electrically conductive projections; anddirectly bonding the gold-containing material to the electricallyconductive caps.
 5. The method of claim 1 wherein the bonding comprises:providing gold-containing balls between the electrically conductiveprojections and the electrically conductive caps; directly bonding thegold-containing balls to the electrically conductive projections; anddirectly bonding the gold-containing balls to the electricallyconductive caps.
 6. The method of claim 5 further comprising formingdeformable material over the electrically conductive caps prior to thebonding of the electrically conductive projections to the electricallyconductive caps, wherein the gold-containing balls are bonded to theelectrically conductive caps prior to the bonding of the gold-containingballs to the electrically conductive projections, and wherein theelectrically conductive projections are pressed through the deformablematerial to directly contact the balls prior to the bonding of theelectrically conductive projections to the gold-containing balls.
 7. Themethod of claim 6 wherein the deformable material comprises anon-conductive film.
 8. The method of claim 6 wherein the deformablematerial comprises a non-conductive paste.
 9. The method of claim 6wherein the deformable material comprises an anisotropically conductivefilm.
 10. The method of claim 6 wherein the deformable materialcomprises an anisotropically conductive paste.
 11. The method of claim 6wherein the deformable material comprises an organic solderabilitypreservative.
 12. The method of claim 1 wherein the electricallyconductive bond pad regions comprise one or both of Al and Cu; andwherein the electrically conductive caps include one or more of Ag, Au,Co, Cr, Cu, Ni, Pd, Pt, Ta, Ti, V and W.
 13. The method of claim 1wherein the electrically conductive bond pad regions comprise aluminum;and wherein the electrically conductive caps include a second layer overa first layer; the first layer comprising nickel and the second layercomprising gold.
 14. A method of assembling an integrated circuitpackage, comprising: providing a semiconductor die having integratedcircuitry associated therewith, the die comprising electricallyconductive bond pad regions and electrically conductive caps over thebond pad regions, the electrically conductive caps being along a topsurface of the die and including at least two different conductivelayers, one of the at least two different conductive layers being aninner layer and the other being an outer layer; providing an interposerhaving electrically conductive projections associated therewith;utilizing vibrational energy having a frequency of at least about onekilohertz to bond balls directly to the electrically conductiveprojections; and utilizing vibrational energy having a frequency of atleast about one kilohertz to bond the balls to the electricallyconductive caps.
 15. The method of claim 14 wherein the balls comprisecopper.
 16. The method of claim 14 wherein the balls comprise gold. 17.The method of claim 16 wherein the bonding of the gold-containing ballsto the electrically conductive projections occurs before the bonding ofthe gold-containing balls to the electrically conductive caps.
 18. Themethod of claim 16 wherein the bonding of the gold-containing balls tothe electrically conductive projections occurs after the bonding of thegold-containing balls to the electrically conductive caps.
 19. Themethod of claim 18 further comprising: after bonding of the gold ballsto the electrically conductive caps, forming a layer of underfill acrossthe top surface of the die and over the gold-containing balls andelectrically conductive caps; and pressing the electrically conductiveprojections through the underfill to directly contact the gold ballsprior to bonding the electrically conductive projections to thegold-containing balls.
 20. The method of claim 19 wherein the underfillcomprises one or more of conductive film, conductive paste,non-conductive film and non-conductive paste.
 21. The method of claim 14wherein the electrically conductive bond pad regions comprise one orboth of Al and Cu; and wherein one or more of the at least two differentconductive layers of the electrically conductive caps include one ormore of Ag, Au, B, Co, Cr, Ni, P, Pd, Pt, Ta, Ti, V and W.
 22. Themethod of claim 14 wherein the electrically conductive bond pad regionscomprise aluminum.
 23. The method of claim 22 wherein the inner layercomprises nickel and the outer layer comprises gold.
 24. A method offorming an integrated circuit package, comprising: forming adhesionlayers over bond pad regions of a semiconductor die; formingelectrically conductive inner layers over the adhesion layers, theelectrically conductive inner layers comprising one or more of B, Co,Cr, Ni, P, Pt, Ta, Ti, V and W; forming electrically conductive outerlayers over the inner layers; directly contacting the electricallyconductive outer layers with electrically conductive structures;directly contacting the electrically conductive structures withelectrically conductive surfaces of a piece separate from the die; andutilizing vibrational energy with a frequency of at least about onekilohertz to bond the electrically conductive outer layers to theelectrically conductive structures; and utilizing vibrational energywith a frequency of at least about one kilohertz to bond theelectrically conductive surfaces to the electrically conductivestructures.
 25. The method of claim 24 wherein the electricallyconductive structures are balls.
 26. The method of claim 25 wherein theballs comprise copper.
 27. The method of claim 25 wherein the ballscomprise gold.
 28. The method of claim 24 wherein the electricallyconductive outer layers comprise one or more of Ag, Au, Cu and Pd. 29.The method of claim 28 wherein the electrically conductive surfacescomprise one or more of Ag, Au, Cu and Pd.
 30. The method of claim 28wherein the adhesion layers are palladium-containing layers.
 31. Themethod of claim 28 wherein the adhesion layers are zinc-containinglayers.
 32. The method of claim 31 wherein the forming of thezinc-containing layers comprises: first zincate activation of surfacesof the bond pad regions to form a first zinc-containing material;removal of the first zinc-containing material; and second zincateactivation of surfaces of the bond pad regions to form a secondzinc-containing material.
 33. The method of claim 31 wherein the bondpad regions comprise aluminum or copper, and wherein the zinc-containinglayers are formed directly against the aluminum or copper of the bondpad regions.
 34. A method of forming an integrated circuit package,comprising: forming zinc-containing layers over bond pad regions of asemiconductor die; forming nickel-containing layers over thezinc-containing layers; forming gold-containing layers over thenickel-containing layers; directly contacting the gold-containing layerswith gold-containing surfaces of one or more pieces separate from thedie; and utilizing vibrational energy with a frequency of at least aboutone kilohertz to bond the gold-containing layers to the gold-containingsurfaces.
 35. The method of claim 34 wherein the gold-containingsurfaces are surfaces of gold-containing balls.
 36. The method of claim35 further comprising bonding the gold-containing balls togold-containing projections of an interposer.
 37. The method of claim 34wherein the bond pad regions comprise aluminum or copper, and whereinthe zinc-containing layers are formed directly against the aluminum orcopper of the bond pad regions.
 38. The method of claim 34 wherein thefrequency of the vibrational energy is less than or equal to 240kilohertz.
 39. An integrated circuit package, comprising: asemiconductor die having a bond pad region surface; a zinc-containinglayer over and directly against the bond pad region surface; anelectrically conductive inner layer over and directly against thezinc-containing layer, the inner layer comprising one or more of B, Co,Cr, Ni, P, Pt, Ta, Ti, V and W; an electrically conductive outer layerover and directly against the inner layer; a gold-containing structuredirectly bonded to the electrically conductive outer layer; and aninterposer having an electrically conductive bump material directlybonded to gold-containing structure.
 40. The package of claim 39 whereinthe gold-containing structure is a ball.
 41. The package of claim 39wherein the bond pad region surface consists of aluminum.
 42. Thepackage of claim 39 wherein the bond pad region surface consists ofcopper.
 43. The package of claim 39 wherein the electrically conductiveouter layer comprises one or more of Ag, Au and Pd.
 44. The package ofclaim 39 wherein the electrically conductive bump material comprises oneor more of Ag, Au, Cu and Pd.
 45. The package of claim 39 wherein: theelectrically conductive outer layer consists of gold; and theelectrically conductive bump material consists of gold.
 46. The packageof claim 39 wherein: the electrically conductive outer layer consists ofgold; and the electrically conductive bump material consists of copper.47. The package of claim 39 wherein the electrically conductive outerlayer comprises a surface; wherein the gold-containing structurecomprises a surface that directly contacts a portion of the outer layersurface and that leaves a gap between another portion of the outer layersurface and the surface of the gold-containing structure; and furthercomprising a z-axis conductive material compressed in the gap betweenthe surface of the gold-containing structure and the surface of theelectrically conductive outer layer.